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TOP-12 JavaScript Advanced Interview Questions

You can easily bolster your chances of success if you prepare judiciously. Be it an interview or an examination hall. You need prudence and clever preparation tricks, and these both are pretty achievable. Below mentioned are some questions that can prove to be of immense help in your following interview.

JavaScript Advanced Interview Questions

 Q.1 Define the specific role of “Close()” in JavaScript?

Ans. The role of “Close()” is quite imperative in JavaScript since it helps the user in successfully closing the current window. However, you have to mention it specifically as “window.close()” to ensure that the given command pertains to the current window object. Otherwise, it might come out as a command for a different JavaScript object than the actual one.

 Q.2 State the difference between “Let” and “Var”.

Ans. Both of the functions are primarily incorporated for variable or method declaration. The pivotal difference between the two is: “Let” is more of a blocked scoped. On the other hand, “Var” is predominantly function scoped.

 Q.3 Explain JavaScript Event Delegation Model briefly.

Ans. JavaScript event delegation is inherently used to lighten things up in the web pages. It is a technique through which you get the ability to successfully connect the sole event handler to a parent element. It is usually done to obviate the need to connect event handlers to several child elements. This model incorporates two imperative features of JavaScript. The first is “Event Bubbling”, and the other one is called “Target Element”.

 Q.4 Elucidate the process of creating an object in JavaScript?

Ans. JavaScript implements the concept of “Objects” exquisitely. “Object Literal” can be used for the formation of an object. The process is described below:

var emp = {
name: “Samuel”,
age: 23

Q.5 Describe the process that is used to form an “Array” in JavaScript.

Ans. “Array Literal” is the most common and predominant method of creating an “Array”. You can form an “Array” by incorporating the steps mentioned below.

var x = [ ] ;
var y = [ 1, 2, 3, 4, 5 ] ;

Q.6 “Name Function” is a common phenomenon in JavaScript. Explain its application in the process.

Ans. When a name is declared in JavaScript, it is done through a named function. This process is briefly done through the use of certain “function” keywords. The whole process is highlighted at the bottom.

function named ( ) {
/ / write code here

Q.7 Explain the function of “Higher Order”.

 Ans. The functions that are classified as Higher-Order are the results of those functions that are tagged as “First-class citizens”.

These functions usually operate on different types of functions. They may use two approaches for this. They may consider them as arguments or simply return them.

 Q.8 Explain the role of “argument objects”.

Ans. We can use the “typeof operator” in such cases. In JavaScript, variable arguments specifically represent the arguments that are further passed on to the function. An example is highlighted below:

function func (x) {
log(typeof x , arguments.length);
func(); / / = = > “undefined” , 0
func (7) ; / / = = > “ number” , 1
func(“1”, “2”, “3”) ; / / = = > “string” , 3

Q.9 JavaScript has different scopes of a variable. Briefly explain such scopes.

Ans. The specific region of the program that is being used and defined is basically the scope of that variable. JavaScript variable encompasses two kinds of scopes.

  • Local Variables: This variable will only be visible inside a specific function where it is being defined. As far as the function parameters are concerned, then they are always local to that particular function.
  • Global Variables: As the name suggests, unlike local variables, these global variables undoubtedly operate on a global scope. It implies that their visibility is not limited whatsoever. They will be visible to you throughout the code of your JavaScript.

Q.10 Describe the method of formulating a cookie through the use of JavaScript.

Ans. For the purpose of creating a cookie, we can simply assign a string value. This particular string value will be attached to the “document.cookie” object. This is how the representation looks like:

cookie = “key1 = value1; key2 = value2; expires = date”;

Q.11 What is the method that you can use in JavaScript to successfully convert the string of base into an integer?

Ans. A specific function known as “parselnt()” is incorporated. Whenever the requirement of converting the numbers into separate bases emerges, “parselnt()” is used. The string that has to undergo the conversion is regarded as the first parameter. Furthermore, the base of the mentioned string is regarded as the second parameter. An example of the given condition is mentioned below:

parseInt(“4F”, 16)

Q.12 Define the role of Exports and Imports in JavaScript.

Ans. Whenever we have to write the modular JavaScript code, Import and Export is the primary function to carry out this task. The major benefit of this function is that we can easily bifurcate our code into more than one file.

/ / - - - - - - lib.js - - - - - - </ span >
export const sqrt = Math.sqrt;</span>
export function square (x) {</span>
return x * x;</ span>
export function diag(x, y) {
return sqrt (square(x) + square (y) );
/ / - - - - - - main.js - - - - - - </span>
{ square, diag } from ‘lib’ ;
log(square(5)); / / 25
log(diag(4, 3)); / / 5

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